BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the present device can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is a longitudinally cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention;
FIG. 2 is a transversely cross-sectional view of the heat pipe of FIG. 1, wherein the heat pipe forms a honeycombed wick structure arranged at an inner surface thereof, and the wick structure includes a waved slice and a planar slice;
FIG. 3 is an enlarged, expanded view of a portion of the planar slice of FIG. 2;
FIG. 4 is an enlarged, expanded view of a portion of a planar slice of a heat pipe in accordance with a second embodiment of the present invention;
FIG. 5 is an enlarged, expanded view of a portion of a planar slice of a heat pipe in accordance with a third embodiment of the present invention; and
FIG. 6 is an enlarged, expanded view of a portion of a planar slice of a heat pipe in accordance with a fourth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a heat pipe in accordance with a first embodiment of the present invention. The heat pipe includes a sealed hollow metal casing 100 having an inner surface and a honeycombed wick structure 200 arranged at the inner surface of the casing 100. The inner surface of the casing 100 may be smooth or may define a plurality of micro-grooves therein.
The casing 100 includes an evaporating section 400 and a condensing section 600 at respective opposite ends thereof, and an adiabatic section 500 located between the evaporating section 40 and the condensing section 600. The casing 100 is typically made of highly thermally conductive materials such as copper or copper alloys. The honeycombed wick structure 200 is saturated with a working fluid (not shown), which acts as a heat carrier for carrying thermal energy from the evaporating section 400 toward the condensing section 600 when undergoing a phase transition from liquid state to vapor state. A vapor channel 300 is defined in the casing 100 along a lengthwise direction of the heat pipe.
Referring to FIG. 2, the honeycombed wick structure 200 comprises a first slice 210 attached on the inner surface of the casing 100 and a second slice 220 attached on the first slice 210. In this embodiment, the honeycombed wick structure 200 has a multiple layer structure consisting of a plurality of alternately stacked first slices 210 and second slices 220 along a radial direction of the heat pipe.
Each of the first slices 210 has a wave-shaped configuration when expanded, consisting of a plurality of triangular sections (not labeled) arranged along a circle. Each of the second slices 220 has a planar type configuration when expanded, and is wrapped into a circle sandwiched between two first slices 210. The first and second slices 210, 220 respectively define a plurality of pores (not shown) therein to form the honeycombed wick structure 200 with a plurality of micro-channels 211 therebetween for reflowing of the condensed liquid. The condensed liquid can flow from one micro-channel 211 to a neighboring micro-channel 211 via the pores. The first and second slices 210, 220 are made of metal sheets.
Referring to FIG. 3, each of the second slices 220 forms a plurality of elongated protrusions 222 at a top surface thereof along the lengthwise direction of the heat pipe. Each of the protrusions 222 includes a pair of opposite and symmetrical lateral walls 224 extending along the lengthwise direction of the heat pipe. Each of the lateral walls 224 has a wave-shaped configuration. A plurality of liquid channels 230 are defined between two adjacent protrusions 222 for providing passage of the condensed liquid from the condensing section 600 to the evaporating section 400. The liquid channels 230 are communicated with the micro-channels 211. A cross section of each liquid channel 230 varies periodically with alternate small and large sections 231, 232. When the condensed liquid flows through the small sections 231 of the liquid channel 230, the velocity of the condensed liquid is increased. By the provision of the discrete small sections 231 of the liquid channel 230, the condensed liquid can be accelerated to flow through the liquid channel 230, whereby the condensed liquid can be speedily transported from the condensing section 600 to the evaporating section 400 via the micro-channels 211. Accordingly, the dry-out problem of the heat pipe can be solved; furthermore, the heat dissipation efficiency of the heat pipe can be promoted. The protrusions 222 can also be formed on the first slices 210.
Specifically, when the working fluid contained in the honeycombed wick structure 200 receives heat from a heat source in thermal connection with the evaporating section 400 of the heat pipe and turns into vapor, the vapor is quickly transferred toward the condensing section 600 via the vapor channel 300. At the condensing section 600, the vapor releases its heat and turns into liquid. Then, the condensed liquid is brought back, via the honeycombed wick structure 200, to the evaporating section 400 of the heat pipe where it is available again for evaporation.
Due to the honeycombed wick structure 200 being made of the first and second slices 210, 220 having the plurality of liquid channels 230 therein which have the plurality of narrow sections 231, the velocity of the liquid can be increased as flowing through the micro-channels 211 of the honeycombed wick structure 200. Moreover, porosity of the honeycombed wick structure 200 is relatively easy to control by regulating the configuration of the protrusions 222, and the number and size of the pores defined in the slices 210, 220; accordingly, heat transfer performance of the heat pipe can be further improved.
FIG. 4 illustrates a second slice 220a of a honeycombed wick structure of a heat pipe in accordance with a second embodiment of the present invention. In this embodiment, protrusions 222a are formed on both top and bottom surfaces of the second slice 220a along a lengthwise direction of the heat pipe. The protrusions 222a have the same configuration as the first embodiment. The protrusions 222a alternate between the top and bottom surfaces of the second slice 220a. Thus the second slice 220a forms a plurality of liquid channel 230a each having a varied cross section periodically to improve the flowing speed of the condensed liquid through the micro-channels 211. In addition, the protrusions 222a can also be formed on both top and bottom surfaces of the first slice 210.
FIG. 5 illustrates a second slice 220b of a honeycombed wick structure of a heat pipe in accordance with a third embodiment of the present invention. In this embodiment, the second slice 220b has a plurality of protrusions 222b formed thereon in a plurality of rows along a longitudinal direction of the heat pipe. Each of the protrusions 222b has an oval configuration with long and short axles. The protrusions 222b are slantwise arranged on the second slice 220b in such a manner that the long axes of two laterally neighboring protrusions 222b form an included angle therebetween. The protrusions 222b of two laterally adjacent columns have a mirror-symmetric pattern so that a liquid channel 230b with periodically reduced sections (not labeled) is defined between the adjacent protrusions 222b of the two laterally adjacent columns, thereby to accelerate the velocity of the liquid flowing through the liquid channels 230b, and accordingly the micro-channels 211.
FIG. 6 illustrates a second slice 220c of a honeycombed wick structure of a heat pipe in accordance with a fourth embodiment of the present invention. Protrusions 222c formed on the second slice 220c have characteristics similar to that of the protrusions 222b of the third embodiment. However, protrusions 222c each have a trapeziform shape. A liquid channel formed between two neighboring columns of the protrusions 222c has alternate large and small sections; thus, the condensed liquid can be accelerated to flow through the liquid channels, and accordingly, the micro-channels 211 of the honeycombed wick structure when flowing from the condensed section 600 to the evaporating section 400.
The protrusions of the previous embodiments of the invention can also be round in cross section shape, although other shapes such as triangular or crescent or the like may also be suitable, only if the protrusions allow the cross section of the liquid channel to vary along its extending direction.
It is known that porosity of the wick structure is an important parameter for the heat transfer capacity of the heat pipe. The honeycombed wick structure 200 of the invention is made of the plurality of first and second slices stacked together and having the plurality of protrusions thereon, whereby the porosity of the honeycombed wick structure 200 can be accurately controlled to improve the heat transfer performance of the heat pipe.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Patent Application
20070277963
